The use of single-domain antibodies (sdAbs) as single antigen-binding proteins or as an antigen-binding domain in larger protein or polypeptide offers a number of significant advantages over the use of conventional antibodies or antibody fragments. The advantages of sdAbs include: only a single domain is required to bind an antigen with high affinity and with high selectivity; sdAbs can be expressed from a single gene and require no post-translational modification; sdAbs are highly stable to denaturing agents or conditions including heat, pH, and proteases; sdAbs are inexpensive to prepare; and sdAbs can access targets and epitopes not accessible to conventional antibodies.
There are a number of diseases or conditions, such as viral infections or cancer, that are caused by aberrant intracellular or transmembrane components such as nucleotides and proteins. Elimination of the aberrant components can be used to prevent or treat the diseases or conditions. There are a number of pharmacological compounds available for treatment of such diseases, but the compounds can be ineffective, undeliverable, or toxic to unaffected cells.
Other treatments include the use of therapeutic proteins or agents that contain an exogenous targeting sequence so that the therapeutic agent can be recognized by receptors in the cell membrane, enabling the therapeutic agent to cross the cell membrane and enter the cell. Once the therapeutic agent is inside the cell, the therapeutic agent can interact with the target component in order to treat the disease. However, the use of exogenous targeting sequences can limit the cell type that is targeted by the therapeutic agent, and adds to the cost of manufacturing the therapeutic agent.
For the foregoing reasons, there is a need for compositions and methods to treat or prevent a disease that do not rely on exogenous targeting sequences or chemical compositions in order to enter the cell, and that are effective in targeting only the affected cells in the body.
The present invention relates to single-domain antibodies (sdAbs), proteins and polypeptides comprising the sdAbs. The sdAbs are directed against targets that cause a condition or disease. The invention also includes nucleic acids encoding the sdAbs, proteins and polypeptides, and compositions comprising the sdAbs. The invention includes the use of the compositions, sdAbs, proteins or polypeptides for prophylactic, therapeutic or diagnostic purposes. The invention also includes the use of monoclonal antibodies directed towards the sdAbs of the invention.